Also in this week's column:
The Minamata disaster - 50 years on
What is deep vein thrombosis?
Can leaving a baby to 'cry it out' cause brain damage?
Is there any evolutionary advantage in snoring?
Asked by John Edwards of Hitchin, United Kingdom
We have addressed snoring many times in many ways.
Points we have not made so …

COMMENTS

Neutral evolution

Genetic drift in evoltution can occur in evolution through natural selection as a result of not only a positive trait, but from a neutral one. The a trait mutates that does not give any significant advantage or disadvantage to an organism, it can continue to exist and can spread through the population. This spread will not be as quick as a gene providing and advantage, as it is a less active (or passive) process.

In the case of snoring; Yes, a noise indicating sleep could alert predators (or aggressive organisms of the same species) that an animal is sleeping, implying that it is the safest time to attack. However, the number of instances where this can occur may remain minimal, making the trait relatively neutral over the total population.

I'm no expert when it comes to snoring. It would be interesting to see at what level snoring evolved. I know dogs snore, although I've never seen a cat do it. I would imagine all primates will.

Because it doesn't limit your re-production ...

In response to "So how has this noisy behaviour survived natural selection?"

The answer is actually fairly straightforward. Natural selection isn't actually about whether or not a trait gets you killed, but whether or not a particular trait increase or decreases your chances of passing on your genes.

The snoring won't actually stop you passing on your genes directly [I snore like a trooper according to my good lady wife - but have still managed to pass on my genes at least once!].

More importantly is the fact that it generally exhibits in later life ("Later" being defined as "some time after puberty", ie after the stage where you could have started passing on genes) there's a good chance that you'll reproduce *before* your nocturnal nostril noises bring you to the attentions of Malcolm the Mastadon ...

So, while the trait doesn't help you pass on genes, neither does it hinder you (Since by the time it's negative influences come into play you can have already passed on your genes - the snoring ones included!)

I heard an evolutionary explanation for snoring -

The explanation was that it is an advantage for hunting animals to sleep and wake together. So snoring is a signal to the pack that everyone needs some shut eye. Then the pack will wake together and hunt as a pack more effectively.

This seems reasonable to me and fits two other aspects of snoring. 1. It is catching, which it would have to be to get the whole pack sleeping. 2. It is animals that hunt in packs that snore - dogs, lions, humans.